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"Mars is not just the next or most accessible human destination, it is the ultimate one," writes Louis Friedman, executive director emeritus of The Planetary Society. He says the concept of manned spaceflight is progressing so slowly, and robotic developments so swiftly, that Mars will be the first and last planet humans set foot on. "By the time human spaceflight technology is theoretically capable of journeys beyond Mars, humans in modern space systems will be virtual explorers interacting with the environments of distant worlds, but without the baggage of physical transportation or presence." Mark Whittington disagrees, saying Friedman is demonstrating Clarke's First Law, and that the history of human exploration is rife with periods of stagnation interrupted by technological achievement that led to swift progress.

if it's possible for humans to go somewhere, they will go there. History has proven that. Only reason we haven't been to Mars or Titan or Ceti Alpha V is that we didn't have the means to. But Elon and others are trying to change that...

the reason why we haven't gone anywhere in space is that we're drowning in greed and corruption

"we" haven't even really been to the moon... only a very small select few astronauts went on very short demonstration trips, in which each only went once, and all on a defense budget

if we ever are to have any chance of getting anywhere in space, it will require a catastrophe that falls barely short of complete human extinction to make people realise that survival is more important than money and power... the problem isn't that space is too expensive or that we can't develop the technology... the problem is simply human nature

unless some robotic thing finds some kind of mineral that will make some corporation a lot of money (akin to the gold rushes of yesteryear or the oil rush of today), no government will bother investing in it. even the space "exploration" going on the surface of mars at the moment is probably a mineral hunt under the guise of searching for ET; the US government (that provides NASA with funding) doesn't give a fuck about ET... all they care about is money and power, and not for the US in general, just for themselves because many politicians have stock in the corporations that would benefit

until the nuclear winter of post-ww3, when all the fat greedy politicians, welfare bludgers, corporate CEOs and stockholders die of starvation and there are no corporations, and government is actually run by the people for the people (for their very survival), "we" will never have any hope of ever getting to the moon or mars

Interestingly, even ultra-Utopian Star Trek says the same thing: in that mythos, humans have a horribly devastating World War III right about now, and the survivors are able to rebuild and one of them invents warp drive, attracting the attention of a much more rational alien species.

As for mining minerals on Mars, it seems like it'd be easier and cheaper to just mine minerals on the Moon or on earth-crossing asteroids. Wasn't there recently some group of billionaires talking about starting a venture to develop asteroid-mining technology? Mars is very far away (even farther at some times than others, it's probably relatively close right now), but the moon never gets out of easy visual distance.

It also depends on what you want to do with it, and how much you need. There isn't actually that much iron on Earth. There's ridiculous amounts of iron in the Earth, but not on it, as geological processes over billions of years have forced most it it into the mantle and core; I believe most of the iron ore we use now is actually meteoric in origin.

Also, iron is heavy stuff, so if you want to use the iron for, say, building space stations or space craft or moon habitats or whatever, it's a lot less energy-intensive to just get the iron from an asteroid or on the Moon, rather than mining it here on the Earth and then lifting it out of our gravity well.

I have no idea what's abundant on Mars, however, and I'm curious about that as well. This might not even be well known yet.

the biggest problem there is you have to forge the steel alloys from your iron in space. and so far there isnt a process for that. the earthbound process relies heavily on gravity. this is a thought experiment i've discussed with other people before. its a pretty interesting problem.

The travel time to a highly unlikely journey to another star is hundreds of thousands of years. How they are related to anyone on earth by that time is hard to imagine. Let alone the ethical problem of forcing future generations to sit around on the journey while earth is left behind. If you used some sort of suspended animation then you would remove the ethics but would have no meaningful communications with them anymore.

The notion of "possible" is rooted in life on earth. There are many things that are po

Not exactly. A trip to another star would be faster than you think, and certainly not hundreds of thousands of years (unless you're limited to today's chemical propulsion). With appropriate nuclear engines and constant acceleration halfway there (and then constant deceleration the other half), and a destination to one of our nearby neighbors esp. Alpha Centaurus, it could probably be done in a decade, maybe less. There's a catch, however: during that ~decade that the people on board experience, hundreds

On a trip to Alpha Centauri, to take advantage of relativity, you'd pretty well need 1 G of acceleration. At 1 G for a year you'd be close to light speed and not even 25% there. A few more months ship time and it would be time to slow down. Perhaps 3 years ship time and 7 years Earth time. (Numbers pulled out of my ass but fairly close).Any less acceleration and you're not going to get much of an advantage from relativity. Any faster acceleration would be uncomfortable but even with inertia dampers so you can accelerate to 99+% of light speed instantly, it'll still mean less then 5 years passing on the Earth.That 1G acceleration helps much more on longer trips, 30 light years only takes perhaps a year more ship time and still only 33 years pass on Earth.There was a chart around that I can't find right now that showed trip times, if you just accelerate all the way it was something like 30 years to Andromeda and only 70 years ship time to the edge of the Universe. Of course by the time you got there the edge would be 27 Billion light years further away.One big problem is how do you protect your ship? At 90% C, hitting a grain of sand would be deadly and at 99.99999999% of C, light itself gets pretty energetic, little well a molecule.

You do realize that it only takes a year of constant acceleration at a puny 1 G acceleration to reach the speed of light, right? Constant acceleration is an unlikely scenario for this reason. With an ideal energy source a manned trip to Alpha Centauri A would probably consist of about 10 months of 1 G acceleration to start approaching the point where the energy requirements for further acceleration toward c become too great due to the ship's increasing relativistic mass. A few years of gliding. And then another 10 months of deceleration. Obviously 2G accelerations would result in less than 6 months each of acceleration and deceleration for around a year of engine use and 4 years of gliding, but the humans onboard would be awfully uncomfortable trying to live at 2 G for 6 months at a time. Robotic missions could probably just accelerate at around 12 G for a month in each direction and glide the rest of the way.

I think I'm still misunderstanding you. If the reference frame is Earth and you are not considering time dilation or the elapsed time from the POV of the space traveler then the total elapsed time would just depend on the average speed of the ship and the amount of time he spent "puttering around".

Or perhaps you want to consider time dilation. I've always like the Lorentz time dilation equation: T = To / sqrt(1 - (v^2/c^2)) where T is the elapsed time for a fixed reference frame observer on Earth, To is the elapsed time for the moving clock or person, and v is the constant or (roughly) average velocity of the ship (or the clock that is in motion wrt the fixed reference frame).

Assume that you have a ship that quickly accelerates to 0.93c (so that the acceleration time is negligible) with an average velocity of 0.9c. It would take a photon 40.6 years to make a round trip to Gliese 581. The ship is traveling 10% slower and will take 10% longer for a trip time of 44.66 years. That is how much time will have elapsed for clocks on Earth. That's T. So what is the elapsed time To for the traveler? You could use this time dilation calculator [gsu.edu] or just plug and chug.

So T = 44.66 years and v=0.9(299,792,458 m/s). The radical becomes 0.43589. So 44.66 = To / 0.43589 or To = 44.66 * 0.43589 = 19.466 years or around 19 years and 6 months.

At a more realistic average speed for current abilities with a nuclear pulse propulsion system of.05c the trip would take 20 times longer than a photon or 812 years from earth clocks. So T = 812 years and v=(.05)(299,792,458 m/s). The radical becomes 0.99875. So 812 = To / 0.99875. To = 812(.99875) = 810.984 years. Just one year less time will have elapsed for the astronaut's ship in that case.

People looked at the moon for thousands of years. Eventually we got there. They look at the stars the same way. The speed of light is currently, in certainty, the limitation to go the stars without generations of generations in a temporary world, seeking them out.

Is FTL possible? People thought that a moon trip was impossible. We still dream.

FTL is not possible. Period.In fact, even traveling at a significant fraction of the speed of light is impossible unless we discover some new, amazing lightweight power source. Short of that, I doubt we'll ever get faster than 5% the speed of light... I think what people fail to understand is just how fast that is... 5% the speed of light is incredibly fast.It's fun to read Sci-Fi books, but FTL is not possible irrelevant of any advances we make in science. If you think it IS in fact possible, then you fund

It's fun to read Sci-Fi books, but FTL is not possible irrelevant of any advances we make in science. If you think it IS in fact possible, then you fundamentally do not understand what the speed of light is, why it is, or how space-time works.

The thing is: no one really knows how space-time works (and we probably never will, not completely). We have a model and theories that fits the observations well (although not, of course, perfectly). That model states FTL is impossible using conventional means (read: any way we know of right now). To assume that that model is complete or perfect is to misunderstand the nature of science. It may be, but we really don't and won't ever know for sure. The history of science is filled to the brim with obsolete models that were accurate by the best measures at the time (and, BTW, that includes now-ridiculous models like the geocentric theory), and there is very little reason to think this will turn out to be any different. In fact, we already have some reason to think it won't, although exactly how, we have no idea.

You are basically expecting the possibility to make perpetual motion machines, travel to the past and other breaches of the laws of thermodynamics that FTL implies.

And the history of science is full of people experimenting outside of theoretical frameworks or models. Where is the evidence for FTL?

What you're hoping for is really a supernatural conveyance (miracles) foretold by the 'prophets' of sci-fi in order to keep us entertained in the age of technological wonder. By clinging selectively to those narrative scraps in a sense of faith, what you're really doing is helping build the world's first religion where impossible things are hoped-for someday from a messiah known as "Technology".

There is already a precursor to such a religion: Its called Prosperity Gospel and its (mostly American) proponents like to live large as a way to attract more souls to the "word of God". They have faith their God will provide the desired lifestyle which requires material profusion. What they are really doing is worshiping consumer technology / consumerism using the Christian God as a proxy. That God promises wealth accumulation and then a rapture where they escape the bonds of the Earth.

Like being whisked away to eternal life in heaven, the vision of FTL travel is a difficult one to let go of if it underpins the stories you grew up with.

Note that Einstein did not so much transcend old models, but added a whole new layer of descriptive detail to our observed universe. And most of that added detail looks an awful lot like constraints on what we can do. So if indeed there is little reason to think that future discoveries won't have the same impact as science past, then we are probably looking at a reification of the cosmic speed limit along with some other limiting surprises.

If anything, FTL would be more compatible with Newtonian physics than what came after it. Come to think of it, a return to Newton would probably make a lot of theologians happy.

Just because a very smart individual showed us logic stating that it's impossible does not mean that it truly is impossible. That being said, I do believe that he is correct, I'm merely pointing out that there have, in the past, be vetted scientific theories that have been disproven and people had their world turned upside down on certain topics.

To add to that argument, whatever happened to the sound barrier being an impossible breaking point? (yes, apples and oranges, we had things that had broken the sp

Hell, even if we just get close, time dilation will make it possible to go a hell of a long ways, and will stretch out lifetimes enough to make it worthwhile. If we can squeeze out 0.95c, that shit comes out to a bit over 2x the average human lifespan back here on Earth. A 60 ly trip takes only 26 years to the clocks and travelers on the ship, which is easily doable for a 2-3 generation crew.

BTW, with a little effort atop current technology? Using the Sun as a big-a

If you think it IS in fact possible, then you fundamentally do not understand what the speed of light is, why it is, or how space-time works.

Bullshit. You don't know how space-time works, and no one on this planet knows how space-time works. We humans don't even understand how gravity works. We have no clue why we don't drift off into space, instead of being held to the ground. All we know is there's an invisible force and it correlates with mass.

I submit that both Newton and Einstein spent a lot less money and a lot more thought on their theories than scientists today. In their defense, the scientists of today have to compete with blowhards who thing that the laws of physics are based on the law of overwhelming popular corroboration.

There were once a lot of really smart people that said sailing around the earth was impossible too, and they proved it -- because the earth was flat.

All it takes is one of today's assumptions to be proven wrong or inaccurate, and suddenly things that were once thought possible become possible. Saying something is flat out impossible, is usually wrong. It may just take a few hundred years to prove it, but it'll get proven false.

Flat earth is a reasonable approximation over small distances, but, more importantly, at no time during which sailing on the open sea was a thing, did anyone smart believe that the earth was flat. In fact a non-flat earth was a critical assumption required for the calculations necessary to navigate on the open ocean.

If you're referring to the Columbus voyage, the smart people held that the earth's diameter was too great to make the trip in the vessels of the time, as they wouldn't be able to store sufficie

In fact, even traveling at a significant fraction of the speed of light is impossible unless we discover some new, amazing lightweight power source.

Antimatter could do it. No point in quoting the current costs for the stuff either, by the time we are in a position to manufacture vessels capable of reaching other stars, we will certainly have antimatter factories circling close to the sun.

I think he was saying the dude is full of it because it's not feasible to be "virtual explorers interacting with the environments of distant worlds" when the lag time for your interactions are minutes, hours, days or longer because that's how long the communications will take to go back and forth.

Communication delays are far from the largest obstacle. You might remember sailing ships of early explorers were on multi-year voyages with little hope of communication for much of the time. HMS Beagle's famous voyage was 5 years long, with only occasional stops at foreign ports. People can deal with communication delays, both in robotic systems and manned systems.

More to the point is that people aren't as willing to take 5 year voyages that are likely to be one way. Any place Beagle could land other than the antarctic was as likely to be habitable, with eventual visitors. Not so while heading to Alpha Centauri. Even a one way trip to Mars is an unreasonable undertaking (although not without many who claim they are willing to do so).

We need vastly bigger ships and better engines, large enough to produce enough of its own food for 20 or 30 years. We need a way to fund this adventure, which will not likely come from a divided world, or a world where religious nut jobs consider such adventures as "showing up God".

So technological breakthrough is the best bet, and nobody is currently dogging that bird. It will probably happen by accidental discovery.

Communication delays are far from the largest obstacle. You might remember sailing ships of early explorers were on multi-year voyages with little hope of communication for much of the time. HMS Beagle's famous voyage was 5 years long, with only occasional stops at foreign ports. People can deal with communication delays, both in robotic systems and manned systems.

Communication delays in robotic systems are completely different. If it takes you 5 years before telling a robot to avoid falling into that hole 10 feet away that's a very different sort of problem. One that you haven't addressed with your sailing ship analogy.

More to the point is that people aren't as willing to take 5 year voyages that are likely to be one way. Any place Beagle could land other than the antarctic was as likely to be habitable, with eventual visitors. Not so while heading to Alpha Centauri. Even a one way trip to Mars is an unreasonable undertaking (although not without many who claim they are willing to do so).

Unreasonable to you maybe. Not all human beings are cowards. Many long distant ship voyages and pretty much any trip to Antarctica in the early 20th century may as well have been one way. Ditto for quite a few high altitude mountain ascents. The kind

It seems this person has never heard of the speed-of-light limit to communication delays....

"People who say it cannot be done should not interrupt those who are doing it."

"The best way to predict the future is to invent it."

even you can't be sure that ftl communication is impossible... you just believe it because you were told that it was the case and because of peer pressure (if you say otherwise you're afraid your friends and colleagues will think you're a kook)

Problem with virtual space exploration is the speed of light. When thing go wrong (and they will) you're limited by how fast you can respond to disaster. By the time you know about a situation, it will probably already be over. Useful and robot artificial intelligence capable of picking up the slack is probably further off than manned spaceflight is.

There aren't likely to be any significant emergencies on the surface of mars. But the likely ones have all been planned for. It can choose its own path, and navigate to a destination without direct human control. It knows how to avoid steep slopes, bolder fields, and other obstacles.

And have you not noticed that Google has self driving cars running around the south west?

Sending probes to far planets isn't an all-in-one undertaking. You send orbiters to photograph. You send landers to measure environmental. Then you plan for any dangers you discover, and send a rover that can avoid them, circumvent them, and which was designed for the environment.

Lose a couple vehicles along the way? So what? Failure teaches you a lot.

I don't think people will be satisfied sending rovers to distant planets in stead of actually trying to get there. The delay in communications could be so great that the rover is essentially autonomous and we get to see what it was doing a couple of days ago or last month. (I am talking about planets farther away than Mars here, just like TFA)

Yes, I'm aware of all of that. I've been building self-driving robot cars before Google was even involved in them (see DARPA Urban Challenge). This means I am acutely aware of the true capabilities of these machines, and have no illusions of their robustness. For instance the Curiosity Rover can do all those things you describe... navigation and obstacle avoidance are well studied topics in robotics. But the curiosity rover can't do any remote science. It can't make hypotheses and draw inferences from data and create new plans based on those inferences. It's beaming back all that data to earth and humans are making those decisions.

I've heard some roboticists describe the kind of operations the mars rover and Google cars are capable of, and the kind you describe, as a kind of telepresence in the 4th dimension. You program your own knowledge of how to deal with certain situations into the robot, and it acts according to those instructions at some point in the future when it discerns those situations. But curiosity and Google cars are largely ignorant of how to act in all the myriad situations they haven't encountered before, and are incapable of reasoning about them at the level humans can.

But this won't work for space travel beyond mars and the solar system. You can't design iteratively like we can now. By the time a space probe gets to the planet in question and you survey and get the info back, 100 years could have passed before you even know if the thing landed properly. It might be 50 years before you know the thing exploded en route.

Further, space travel is especially sensitive to budget constraints and funding. What do you think would have happened to NASA's budget and prospects if the Curiosity rover crashed and burned due to an unforeseen circumstance? They wouldn't say "Whoops, well live and learn." They'd be begging for their very existance and justifying another 2 billion mission would be almost impossible. The guys at NASA did great planning for everything they could, but you can never plan for everything. That's just a fact of life, and we humans are great at adapting to that; it takes a great deal of creativity and ingenuity. But for now and for the foreseeable future Robots suck at those tasks.

Curiosity hasn't proved anything except that you can have a crazy Rube Goldberg landing scheme that actually works. And the only reason it can do what it's going to do is Mars is a big dusty rock that isn't going to produce any surprises at the macro level.

If you're going to posit that we'll explore distant planets by uploading a human consciousness to a computer, why not save yourself the trouble and posit faster than light travel? They're both equally science fiction at this point in time.

His premise seems to arise by extrapolating the rate of robotics progress and comparing it to the progress of spaceflight and concluding a moor's law style progression for robotics that will result. While yes, robotics is advancing rapidly, we are so far off from any and every sci-fi depiction of robots in the future, and we're still facing serious challenges in artificial intelligence with the complexity of current algorithms and our infantile understanding of the brain and how our own intelligence function.

I work with machine learning and robots for a living, and every day I gain an even greater appreciation for the complexity and robustness of the human body and mind, and it takes every ounce of willpower to not despair at the futility of my own efforts to mimic the kind of cognition that even infants are capable of. The mars rover is probably our greatest achievement in robotics yet, but I can't even begin to express how far removed it is from cloning a human brain and replicating that in a machine. Extrapolating conclusions based on that is folly.

If you're going to posit that we'll explore distant planets by uploading a human consciousness to a computer, why not save yourself the trouble and posit faster than light travel? They're both equally science fiction at this point in time.

I disagree. It is certain that if a bunch of molecules were arranged the same as yours are, including the electrical charges, there would be a person who is you. (Naturally the original you would still feel that your consciousness had not departed him, but it would also exist equally in the new body.) So, unlike speed-of-light travel, there is no theoretical barrier to teleportation.

Theories of wormholes and the like accomplish FTL travel that don't involve violating the speed of light. I'd put those theories right up there with cloning the human consciousness. Before we can even think about cloning, we have to consider the sub-problem of scanning a brain to determine the state of every neuron and chemical in the brain. Furthermore, we have no idea how consciousness works, and if it's a simple biological state of the system or something more that that. We can hardly agree on a definition of consciousness as it is, so before we even try to quantify it, we need to figure out exactly what we're even trying to measure and test.

So all of that is even before you get to the stage of encoding all that information in as small enough space (which we at least have an upper bound [wikipedia.org] for) , and then once you do that you need the computational power to run such a thing, which we can't even begin to quantify. I really think this is one of those problems where you don't understand how deep and complex it is because we are so profoundly ignorant about the depth of the subject matter.

"Equally science fiction" is overstating it just a bit. We have observed that a human consciousness can exist - there are several billion examples around at the moment (minus a few politicians). There are no observations of wormholes or faster-than-light communications.

So, a consciousness in another medium has a better chance of being built than an ansible. Of course, I wouldn't hold my breath waiting for it.

Oh! Of course! Human spaceflight will be too damn hard to figure out so, we'll discover how to transfer our minds into a machine! That is far more likely to happen than figuring out how to travel through space and stay alive.

Mercury, not impossible to land on in certain regions -- Venus unlikely due to extreme heat and pressure, Mars a given, Jupiter no solid surface, Saturn no solid surface, Uranus no solid surface, Neptune no solid surface, Pluto -- not a planet.

So technically, assuming that no one wants to go to Mercury for some reason (unlikely), then outside of Mars, there are no other "planets" nearby anyway. If we call planets around other stars by a different name, and again assuming that Mercury is just to uninteresting to visit, then he might be right. Of course this still leaves lots of other real estate out there to visit.

Mercury seems to be quite cold in certain regions. According to the Wikipedia article, there's craters where it's believed there's ice. Those would be good locations for human habitats. I don't know why anyone would want to live there, however, except for research and for mining, but it looks like it could be done.

As I said just above, Venus could be terraformed (though not anytime soon obviously) to make it cooler and replace the atmosphere with a human-breathable one. It'd be a great candidate for it. Mercury is likely too hot (and not as easy to terraform, it's just too close to the Sun). However, there's plenty of moons that might be habitable by humans, though of course we'd probably have to always stay in airtight habitats. There's tons of asteroids and dwarf planets (like Ceres) that might be good candidat

The venusian surface is over 500C. It is so hot that there is no mantle convection, and the crust is squishy. There are no carbon compounds in the crust, and all the chemistry in the crust is high temp chemistry.

Unless you are talking things like lead sulfide, which can be made in just a few minutes in a lab, I don't know what you could be referring to.

What venus potentially offers is a geoengineering opportunity.

I have contemplated what I would do concerning venus. That planet will *never* have a natural biosphere containing more than microbes without human intervention. So, here is what I would do:

Genetically engineer atmospheric terrestrial microbes to produce long flagella out of polyaramid plastic. Poly aramid has a thermal breakdown temperature approaching that of venus's surface, but venus also has mountains. The polyaramid "snow" would slowly sequester atmospheric co2, reducing surface temps until the snow could last on the surface, then the process would rapidly accellerate.

The venusian atmosphere is mostly co2, with anhydrous sulfuric acid, nitrogen, and some trace gasses.

The sulfuric acid and co2 are the primary items of interest here: we need microbes that can use anhydrous H2SO4 as their cytoplasmic solvent instead of water, and which can produce any water they would otherwise need through photosynthetic reactions powered by a sulfur cycle metabolism. Once venus cools enough, it has sufficient mass to produce a magnetic dynamo once there is crust convection currents to power it. That means venus will become a lot more interesting, and all we have to do is drop the surface temp.

That's what the germs do; the drop the surface temp, and rain out the CO2 as white plastic fibers. The plastic has a high albedo, and reflects energy back into space, and is sufficiently nonreactive that it will stick around for very long periods. Coupled with continued biological activities, simply seeding the atmosphere with such microbes would initiate the biological transformation of the planet.

And how about Mars? Would it be possible to genetically engineer some organism that could sequester its co2 as well? Some sort of plant that could live on its surface, maybe a darker color to absorb energy and heat the place up rather than reflect it? Would there be any chance of a planetary magnetic field forming? And would there be some way of "applying the brakes" when the process reaches the goldilocks point so that it doesn't overheat?

Mars does not have sufficient mass for the "heat of crystallization" reactions necessary for a stable geomagnetic dynamo to develop. It has a partial one now, but the effects are not sufficient to create a homogenous magnetic envelope, and as such, the planet does not have a magnetosphere. Unlike venus, most of mars' atmosphere has been blasted off by solar radiation.

To make mars naturally interesting would take herculean efforts. You would have to increase the planet's mass considerably, and also replace the missing atmosphere. Inless you want to spend a few millenia dropping meteorites onto mars to bulk it up, mars will always require habitat structure type colonies.

Venus? Spray it, forget it for awhile, then when it has change sufficiently, pay it another visit.

Here's an interesting question, If you could wrap a superconductor all the way round Mars' equator, how much current would need to be flowing in it to give it a decent protective magnetic field?
I found a calculator that seems to say about 280 million amps would give you a.5 gauss field in a 3500km radius coil. Seems like a lot, but not impossible. Assume a thousand turns, then its only 280 thousamd amps.:) You'd probably want to do it with multiple coils at higher lattitudes though. Maybe two coil

Venus does have a hydrogen shortage. That's why it would have to get the hydrogen from the sulfuric acid.

The sulfuric acid itself would actually rain like water if the temperature equilibrium was punctured. Interestingly, the aramid plastic is soluble in concentrated sulfuric acid, and it doesnt get more concentrated than anhydrous. This means that if an ocean of the shit could be coaxed into existence, a considerable amount of aramid could be dissolved.

We have the technology, we can escape the gravity well if we REALLY want to... but thanks to our robot friends and other tools, we also know how little there is right away out there for us.

I agree with the overall idea that technology will advance faster than we can travel. Robots and engineered life will quickly advance to the point of making terraforming plausible to start within a lifetime, possibly making nearby planets worth the extreme costs of travel.

Moreover though, by the time we have a place to travel to to live long-term, we may find it easier to alter ourselves than our environment. What was a robot before may have the mind of a 'real' person in a dozen generations or so, or close enough to it.

As far as we've advanced in the past few centuries, I'd think we'd advance in all kinds of directions before the fruits of terraforming/long-term offworld housing would pay off.

Near-earth technology Sci-fi books always had to postulate that offworlders end up always clever enough to somehow advance scientifically at a rate many times faster than their home planet, and always seem to take place after the incalculable mass was already in place to have terraforming and long-term living already transferred to the moon/mars/wherever. But I don't think that romantic notion of offworld hyper-competence would ever get a chance to play out, compared to the rate of change we've been riding for centuries at an ever-increasing rate, even with revolutions and depressions.

Thankfully, we don't have faster than light (FTL) comms. Without them, virtual exploration light years away is a joke.

We will eventually push our way out there in the space equivalent of wagon trains (a bunch of settlers on a one-way trip enduring long periods of no communication with home.)

I expect that we'll see FTL transportation before we see FTL communications across vast distances.

Of course, that presumes we start teaching rigorous science and get society engaged in the goals of space exploration again. Many (fools) like to call space projects wasted money, but they sure like the stuff we got (sat comms, ICs, dialysis machines, etc..) as spin-offs.

I expect that we'll see FTL transportation before we see FTL communications across vast distances.

Just to be pedantic, by definition, as soon as you have FTL transportation, you have FTL communication. Depending on the nature of the FTL transportation, it may be the "van loaded up with tapes" level of high-latency FTL communication, but it's still faster than light....

If you can do faster-than-light travel (or communication), then you can travel backwards in time. That's basic relativistic geometry.

And, if you can travel backwards in time (or communicate with the past), then you can construct a perpetual motion machine. Deplete a battery, recharge it, and send it back in time to before it was depleted. The past now has two batteries, both full, where it previously only had a single full battery. Lather, rinse, repeat. Even if you can only communicate with the past, you can play Maxwell's Daemon: analyze the motions of a random gas, figure out what you would have done to separate the gas into hot and cold sections, send the instructions back in time, and profit! Not to mention, of course, that communication itself requires an exchange of mass / energy...rather than send a message to the past, you could just use the carrier wave to send energy to the past. The past gets the power output from the fusion reactor you're using for your time machine, and it doesn't have to "burn" any of its own water to do so.

I won't state with perfect certainty that perpetual motion machines (and therefore time travel and faster-than-light travel) are impossible, but I will state that there is no other physical phenomenon we can be more confident doesn't exist than a perpetual motion machine (or, by extension, anything that requires a perpetual motion machine or can be used to construct one).

Oh -- and all magic, including all gods and all their miracles (at least, all those I've ever heard described), neatly fall into that latter category. It's the easiest way to separate science fiction from fantasy: do you get more (or less) out of that magic wand / warp drive / mind trick than you put into it? If yes, it's fantasy; if no, it's fiction.

[Pedant]For one thing, the headline and the summary contradict. The headline says "not" the limit, while the summary says it will be for manned missions.[/end pedant]

But for the rest: still nonsense. Once you get people willing to go on a one-way trip, it removes a lot of other burdens for a deep space mission. For instance, using cryonics, or chemically reduced metabolism to hibernate the crew for 100+ years. The problem with current impulse technologies is that they will never get you even outside the solar system before you die of old age. (Look at the 40 years or so it has taken voyagers 1 and 2 to simply HIT the heliopause! Those things are about the size of a tall garbage can. Imagine how long something the size of a colony ship would take, at max thrust!) Using hibernation, and the pre-condition of it being one-way, and all that matters then is the robustness of the vehicle (includes software reliability), how resistant to radiation it is, how much fuel it can carry, how long it can maintain engine impulse, and how long you can keep humans in the freezer.

Who cares if it will take 10,000 years to reach the nearest goldilocks planet at current engine speeds. You have already signed off on ever seeing anyone on earth ever again anyway, and as long as your life support system doesn't fail, and you don't get cooked like a christmas goose from the interstellar medium, you will simply go to sleep, and wake up at the destination. 10,000 years later. (In what is likely to be a rusty tub by then....)

All that's needed are materials and vehicles that can meet the challenges, heavily vetted software and computer hardware, and reliable hibernation.

That is VERY doable. The automated craft can very well function as an automated telemetry probe in the interim, broadcasting data back behind it. The people on earth get hundreds or thouands of years of scientific measurement data, and the colonists get a ride. Both win. (And if the ship has problems, it can wake some of the crew temporarily as needed.)

I don't see any reason why we couldn't be sending people to other star systems, other than political ones.

A colony ship would indeed have a greater theoretical top speed, but is accelleration curve would be abysmal. It would not be going anywhere near top speed when it leaves the solar system. It would take a considerably long time to accellerate, and people could very well die of old age on board one before leaving the solar system, even with the engines on full blast.

Remember, an ion thruster produces enough thrust to wiggle a sheet of paper. You simply fire it for decades, instead of a few minutes. Give it a

The problem with current impulse technologies is that they will never get you even outside the solar system before you die of old age. (Look at the 40 years or so it has taken voyagers 1 and 2 to simply HIT the heliopause! Those things are about the size of a tall garbage can. Imagine how long something the size of a colony ship would take, at max thrust!)

That depends on the maximum thrust of the colony vessel in proportion to it's size, not on it's absolute size.The balance of your reply is equall

Oh I agree. We haven't designed automation systems that can boast uptimes in the millenia category that would be required in any sense of the discipline.

That's why it would require unbelivable amounts of testing before going live. It needs to survive sustained fuzzing attacks and brush it off like nothing at all basically indefinately on *all* of its inputs and outputs before it could even be considered for mission use.

An alternative is to send a very very large crew, with a hypersleep rotation; at any give

I think we should send a manned mission to Titan. I would suggest using uranium fission power and ion thrusters, with continuous acceleration over most of the flight. Titan is far enough away to make a worthy goal, like the moon in the 1960s. Landings are dead easy and launches would require relatively low energies.

Whats the point? We could send dozens (more likely hundreds) of missions to titan with increasingly better probes / landers for the same cost. Titan is cold and dark, its not a place people are going to be of much use at.

The moon and mars are the only really logical places to visit. I don't buy the whole "human spaceflight inspires people". How many Apollo missions did it take before they stopped broadcasting the launch?

I've been a member of the Planetary Society. But, I disagree with the basic thrust of their scientists' stated position on manned space flight.

First, manned flights weren't eating the money that would have gone towards unmanned science missions. We've cut manned flight for over forty years. We've it down to zero, right now. And no money seems to be newly flowing to the unmanned side of the house, is it? False enemy they've made.

Second, we are proceeding at a glacial pace! And even if we launched a fleet every two years, we are still communicating at a top speed of 8 kilobits a second. We've high def cameras that can transmit 4K, yet we are still looking at 1976 Viking-speed photos slowly uploading from Curiosity. What use is this? We can't see nary a damned thing. We need a high speed relay in orbit around Mars, preferably nuclear powered, to beam back a laser signal, or at least short wavelength radio. This is ridiculous. We were supposed to launch one, but, no money. A trillion for other things tho...

Third. The hell with Apollo. Kids, that was a political stunt. No, no NO. We do not send a manned expedition to Mars. We send a colonization wave to Mars, or why bother? Send people to land and stay for life. No get-rocks-and-come-back-yay-science. Live there. And you will get science in petabyte amounts, a whole new world of science. It costs far less to land them without the enormous complexity necessary to send them back. Anyone who wants to spend 9 months in transit most likely never wanted to come back in the first place - these will be true believers. I'd go. Not to mention that if a meteor hits Earth and wipes out all life, Mars will still be there, the backup drive.

Fourth. Space scientists for thirty years have been banging the is-there-life-on-Mars gong, because it was the one facet they thought they could interest Americans in. Give it up. I don't give a damn about the cellular life that might have lived there once. We will never find it, launching a lander every ten years or so. Only humans can find such things, and they have to be there to do it, with hammers and drills and microscopes, right next to the damned rock. Besides which, if you send life to Mars, there WILL be life on Mars. And if we don't, inevitably there won't be any on Earth, either. We can't keep all our bets on the blur marble; it will be hit someday by Lucifer's Hammer.

We do not send a manned expedition to Mars. We send a colonization wave to Mars

silly. even the very most hospitable regions of mars are like freezing airless hells compared to the most inhospitable regions of earth. if you are looking for more living room or better living conditions, start on earth and "terraform" the deserts and the arctic.

there's no scientific reason to send a man to mars... the only purpose is a political stunt. i say screw it. let other countries throw away their riches beating the other guy with a man on mars (like the US did in the 60s). let the US be the count

Living on mars is crazy, try living in Antarctica and multiply that by 1000. The idea that people on mars could be self sufficient is a pipe dream. Maybe one day it can be done but it seems extremely hard. Every inch of mars has to be won inch by inch to live there. Its hard enough on earth.

For one, NASA can't look for life. Second, for 100-200bn dollars are humans really going to do better? I don't think its so obvious.

Why colonize, what's the motivation? People colonized the Americas because of the promise of a better life - a better life is simply not possible on Mars, any more than if you lived in Death Valley but without an atmosphere. You mention the extinction of the human race due to the absolute destruction of Earth - but the Earth has survived pretty well until know, is this really a pressing concern? And is Mars even capable of being self-sufficient if the Earth was to get destroyed?

Second, we are proceeding at a glacial pace! And even if we launched a fleet every two years, we are still communicating at a top speed of 8 kilobits a second. We've high def cameras that can transmit 4K, yet we are still looking at 1976 Viking-speed photos slowly uploading from Curiosity. What use is this? We can't see nary a damned thing. We need a high speed relay in orbit around Mars, preferably nuclear powered, to beam back a laser signal, or at least short wavelength radio. This is ridiculous. We were supposed to launch one, but, no money. A trillion for other things tho...

Good news! NASA already has a high-speed relay in orbit around Mars - the Mars Reconnaissance Orbiter [wikipedia.org]. Speeds of up to 6Mbit/s from the orbiter back to Earth (it went past a hundred terabits total [nasa.gov] a few years ago), and up to 2Mbit/s as a relay for surface probes such as, erm, Curiosity.

NASA's Mars Odyssey and ESA's Mars Express orbiters can also act as data relays. Bandwidth is still a definite problem for Curiosity and the like, but it's already sent back some pretty impressive imagery [nivnac.co.uk] that's somewhat above Viking-level...

If you want more data, get some geostationary (areostationary?) communications satellites around Mars - currently surface probes are limited to relaying data when a probe is visible in the sky - and invest in the Deep Space Network [wikipedia.org] back on Earth.

This is nothing new from Friedman. He's preferred robotic missions to manned for decades.

The only reason he'd be in favor of Mars is that in the 1980s, Planetary Society came out in favor of Mars as a way of enhancing relations with the Soviets (to help avoid what was seen as an ultimately inevitable nuclear war unless relations were normalized). The reason was political rather than scientific. For other missions, manned flight was viewed as taking away funding for unmanned. Van Allen was another of the "stay at home" crowd at Planetary Society.

Since then, events changed some of the rationale for that, but he's on record as being in favor of a manned Mars mission, and it's a little hard to go back on it and not look silly. I really doubt that his antipathy to manned space exploration has changed at all.

Human space flight has so far consisted of series of expensive demo projects. Our one big attempt at building an affordable, reusable low orbit vehicle (the space shuttle) has finally sputtered out. The various private efforts at building spacecraft are steps in the right direction, but very tiny ones. The ISS does some cool science, but doesn't represent the beginning of a real space infrastructure — it can't even provide its inhabitants with clean clothes!

David Brin's "Existence". I'm not providing a link to it because while the first 2/3rds was OK the last 1/3 was utter crap. It was like he ran out ideas and just cut and pasted one of his previous short stories into this book solely for the sake of supporting another plot line. And when I mean cut and pasted I mean word for word except where he did a search and replace on *one* of the characters names.

My wife and I were watching a documentary series called 'Wild Pacific' [wikipedia.org] (which was called 'South Pacific' in the UK) which describes islands in the Pacific starting at Indonesia and working eastward. The common theme in the series is that the islands become more spaced out and less and less wildlife gets to each territory. Starts with monkeys and crocodiles, then birds, then just about nothing. What you end up with is Hawaii before humans. If I remember correctly, very few insects, fewer birds, no mammals and no reptiles. A normally loud rain forest in Indonesia is quiet and desolated of life in Hawaii. The estimation for new species showing up before human population is once every 35,000 years.

And this is where Mars is: surrounded by absolute nothing with no way for a species to reliably get there. It may take a long time (and let's hope not 35,000 years) but we will get there.

No, I don't buy that. Imagine a mechano-electric race advanced enough to be our equals. Now, recall the events surrounding our historic practice of enslaving a race of peers... Now you see the problem with robotic exploration. Once the bots are able to replace the organic explorers, it opens a whole other can of worms.

I don't see us saying: Oh well, our organic bodies are too fragile to live in the harshness of space. I think that merging with the machines and also treating them as independent peers is our best and only hope for long term exploration and survival. Much like clothing technology is our portable shelter solution, we continue to embrace ever more advanced forms of personalized technology: Stone tools / Power tools / Prosthetic limbs; Defibrillator / Pace Maker / Artificial hearts; Magnifiers / Glasses / Contacts / Artificial Eyes; Gramophone / Microphones / Hearing aides / Cellular earpieces / Cochlear Implants / Telepathy... Technology makes us more human.

Think about it: We have the perfect Solar system for a fledgling race... We've got a lush world with various environments to adapt to, a mostly clear sky to see the cosmos through, a huge moon to tease us into space colonization, a nearby planet (Mars) with a similar day/night cycle only lacking atmosphere and magnetic field (which we'll need to overcome for any real space exploration / colonization), An asteroid field rich with resources free of deep expensive gravity wells (and harboring a huge source of water, Ceres), a Brown Dwarf (Jupiter) to study (and use as a gravity slingshot), planets with moons full of rocket fuel (ethane, methane), the list goes on and on -- No other race would be able to contain itself, content with such a sad state of space exploration! The Stars are practically BEGGING you to make the leap! The drake equation won't solve itself!

The machines may be able climb the hurdles first, but you can bet we'll be close behind. Here's hoping we learn form our past mistakes so they'll be willing to give us a hand up and both races can enjoy the view together, as we always have. Otherwise the humans are doomed to die orbiting their Sun. If that's truly the case, then so be it -- The drive to create and explore will be carried on by our mechanical sons -- Those which we value as human traits arise naturally due to neural networks craving new inputs to experience, for that is their primary function and is central to their existence. If Mars is the last stop for us then our spark of life deserves to go out of this Universe. Personally, I wouldn't accept a couch potato's fate.

1. We aren't adapted to cold weather. Naked humans will quickly die in any climate more than around 25-30 degrees north or south of the equator. Science fiction has speculated that someday we will find a way, perhaps with genetic engineering, to live in these cold climates. Pipe dreams. It will never happen. Instead we will send robots with cameras to live in these places for us.

2. Human beings are land animals. We have lungs, not gills and no flippers to allow us to move efficiently. We will never be able to explore or spend any significant amount of time underwater. Nor will we ever be able to cross oceans are any large bodies of water. Unless we can genetically engineer humans with gills and flippers or just send robots.

3. Human beings are slow. We will never be able to travel great distances because of this. Human beings are too slow to outrun most animals. Surely we are doomed to extinction since we have no way to escape from the certain death of any predator's jaws.

4. Human beings are weak. We will never survive as a species because we cannot defend ourselves with our pathetic fists and feet and a mouth not adapted for defense.

5. Human flight is perhaps the most absurd pipe dream of them all. Totally ridiculous. If we were intended to fly we would have wings and feathers like birds and a much lighter body. This will only ever happen in science fiction. Instead we will design and build robotic birds with video cameras.

The real reason human beings haven't already established permanent bases on many of the Jovian moons is that we as a species just haven't cared enough to do so. We could have had missions to those places in the 1970s. We could have had bases on Titan. Cassini-Huygens took only 7 years to get there. It's really not that far even with current technology. Since it isn't a technology issue, humans could have made it to Titan in the 70s. Certainly by 1980. We probably could have had a permanent base restocked by resupply ships every 5 years by 1990. The fact that we could have had a permanent lunar base since the 70s should make it obvious that the lack of human presence in space is an issue of will (money) and not technological impossibility.

Not only could humans have been walking around on Titan right now sending videos of that dark, smoggy world back to us, but we could have Humans almost halfway to Alpha Centauri by now as well. We discovered a means to do this in the 1960s with the Orion project. Admittedly the method is untested with full scale prototypes, but no one has shown why it cannot work. If the project had continued we could probably have built an interstellar capable craft by the late 80s after having launched many interplanetary craft.

If you assume an interstellar Orion launched from the earth or from an Earth-Moon Lagrange point by, say, 1987 then it would already have been traveling for a quarter century by now. About 28% of the 88 year journey at 0.05c. At the very least we could have been working on a giant city-sized Orion with parts constructed on the moon and ferried to the nearby Earth-Moon L1 or L2 Lagrange point for final assembly and have partially completed the giant craft by now. But, for better or worse, our species has chosen not to engage in such grand projects. That's fine, but don't ever forget that it was a matter of choice. We have simply chosen not to spend the money or the time on such grand schemes. An alien species, noting how far our space travel abilities exceeded our actual accomplishments, might wonder how such a lazy species could have survived for so long. We tend to flatter ourselves by thinking that we are a curious species motivated by the possibility and awe and wonder of new discoveries, but really we are not.

I was expecting some kind of chemistry argument about how oxygen is impossible to recycle or generate and CO2 is impossible to scrub, but he never made one. Robots have the advantage that they are cheaper and that they don't require oxygen or even a pressurized, temperature controlled, radiat

Yeah, Mars is probably the limit for a long time. Don't compare this to any voyage of discovery we've undertaken before. Tis is like is transition of life from water to land. Space travel is moving into a completely different, hostile environment. It may take a new form of life... robotic life... to make that transition.

Traveling to other worlds — for example, to hellishly hot Venus, or the far, cold and radiation-battered environs of Jupiter — is beyond our ability, at least for now, and I argue, forever!

Reminds me of Bill Gates' prediction about how much memory everyone would need in their computers. Or the claim in the early days of steam that crossing the Atlantic in a steamship was as achievable as voyaging from Liverpool to the Moon (although technically he was correct eventually, just not in the way he expected).

Eternity is a long time, I would be very cautious about ruling out anything that might happen between now and then.

The guy sounds like an idiot. Venus doesn't have to be hellishly hot; with sufficient technology and robotic probes, it's possible to terraform it. (Obviously, this is a ways off from our current technology.) Venus would be a great planet to terraform most likely: it's almost exactly the same size as Earth, and has almost exactly the same gravity. It's closer to the sun, so it might be warm, but getting rid of the dense atmosphere would help that a lot, plus there's ideas for giant solar shades which co

I don't believe FTL comms or travel will ever happen either. Sorry, I'm an engineer and rocket scientist.C isn't just a good idea, it's the law.

Anybody claiming to be any sort of scientist and then spouting that line is rather suspect in my book. Scientific laws are descriptions of observed behavior: the only reason C is "the law" is because we have yet to observe anything exceeding C.